1. Field of the Invention
The present invention relates to a semiconductor device using a silica film forming coating liquid for forming a silica film and a method of fabricating the same.
2. Description of the Related Art
A degree of integration and miniaturization have recently been increased and miniaturization has recently progressed. With this, a size reduction in an element isolation region has been desired strongly. A shallow trench isolation (STI) structure has been employed in an increasing number of times to meet the needs. The STI structure can sufficiently render the element isolation region sufficiently small. As one of methods of burying a silicon oxide film (SiO2) in an isolation groove in the STI, methods using a polysilazane film are known. For example, Japanese Patent No. 3178412 discloses one of the methods using the polysilazane film.
In the method disclosed in Japanese Patent No. 3178412, an SiO2 film is formed on a surface of a silicon substrate and thereafter, a silicon nitride (SiN) film is formed on the SiO2 film. Furthermore, an isolation groove is formed in the SiN film. Successively, the surface of the substrate is covered with a polysilazane solution (a solution of a silazane perhydride polymer in the above-noted reference) by spin coating. Subsequently, oxidation by substitution is carried out using H2O (in an atmosphere of steam) so that the polysilazane film is denaturalized to an SiO2 film.
The following problem arises when the polysilazane film is applied to STI. In the oxidation by substitution in the atmosphere of steam, H2O reaches the substrate, oxidating the same. Oxidation of the substrate increases a thickness of the gate oxide film. Oxidation of the substrate further shrinks the polysilazane film. When the groove has a large width, the SiO2 film peels off.